A definite no-no for benito
Well, PR-wise he'd be a thorn in the side of mostly Mussolini, but also hitler. The spiritual leader of the catholic church urging his followers to stand by the jewish communities and shelter them from the nazists and to some degree the fascists?
That could potentially give enormous butterflies.
A larger, stronger and more popular resistance to the two dicators in their countries and occupied territories?
Hell, maybe Mussolini himself realizes that joining the deranged nazi-side won't be as awesome as he had thought, and strikes a deal with the pope to stay neutral, accept jewish refuges in return for the pope not condemning facism as particulary evil?
I don't know, this is "guesstimating" you might say, sadly not my area of expertise.